In an active workflow, when you delete a delay that has contacts waiting in it, those contacts will proceed to the action following the next delay after they have waited the full time of the deleted delay.
This can sometimes play out differently for your contacts based on what steps they have already executed in the Workflow before the delay was deleted.
In the example below, we can see the workflow is set up as follows:
Delay 1 > Action: Email 1 > Delay 2 > Action: Email 2
You enroll a contact (Contact A) in the workflow and they are sitting in Delay 1 and are scheduled for the first action in the Workflow. For now, that first action is Action: Email 1.
Now, let's say you add Action: Email 0 to the very beginning of the workflow, making it look like:
Action: Email 0 > Delay 1 > Action: Email 1 > Delay 2 > Action: Email 2
You now enroll another contact (Contact B) in the workflow. Contact B executes their first action in the workflow, receiving Email 0, and is now sitting in Delay 1 along with Contact A.
Let's now say that you delete Delay 1, where both Contact A is awaiting their first action in the workflow, and Contact B is awaiting their next action in the workflow.
When you delete Delay 1, Contact A will proceed through the Workflow by receiving Email 0 and Email 1 at the end of the deleted delay period. Since Contact A has not executed any actions in the Workflow yet, Email 0 and Email 1 become their first two actions in the Workflow once the deleted delay period is over. Contact A will then proceed to sit in Delay 2, scheduled for Email 2.
Contact B, since they have already executed their first action in the Workflow (Action: Email 0) will now advance at the end of the deleted delay period to the action following Delay 2, which would be Email 2.
In Contact B's case, if you want the contact to execute the action directly after the delay you deleted (not the action following the next delay) you can add a new delay of 0 minutes in place of the one you just deleted. Then, that becomes the next delay and the contact executes the action right after it. In this case, that would be Email 1.